In the metallurgical industry, the preheating of air for blast furnaces is conventionally carried out in adjacent regenerative heaters known as hot blast stoves. These stoves generally consist, for a stove with internal combustion chamber, of a cylindrical refractory wall and an internal vertical partition wall partitioning the stove into a combustion chamber and a checker chamber containing checker bricks or, for a stove with external combustion chamber, of two cylindrical refractory lined chambers with a connection dome. Air and fuel is introduced through one or two openings into a so-called ceramic burner or metallic burner in the combustion chamber for burning and the resultant combustion gasses flow upwardly from the combustion chamber over to the combustion chamber downwardly through the checker work chamber until they are finally exhausted at the base of that chamber. As the combustion gasses pass though the checker work chamber containing a plurality of checker bricks, heat from the combustion gasses is transferred to the checker bricks and retained therein. Once the checker bricks have reached a sufficiently high temperature, the direction of fluid flow in the stove is reversed. A cold blast is introduced at the base of the checker work chamber and is fed through the checker work chamber, where the cold blast absorbs heat from the checker bricks and passes over the partition wall and through the combustion chamber, where it leaves the stove through a hot blast outlet in the shell of the stove to be fed to the blast furnace.
Many different designs and arrangements of checker bricks have been designed over the years. An example of such a checker brick design can e.g. be seen in U.S. Pat. No. 4,436,144, which describes a checker brick having an octagonal outside contour and a central through passage of tetragonal cross-section. Furthermore, this brick has a substantially uniform wall thickness. Such bricks are preferably stacked in layers and staggered relative to each other. This results in a stack of checker bricks with vertical passages being formed for the gasses. In order to facilitate stacking of the checker bricks, they are provided with raised portions at the top surface of the brick and with corresponding recesses at the bottom surface of the brick.
Another example of such a checker brick design can e.g. be seen in U.S. Pat. No. 2,017,763, wherein an essentially square checker brick is provided with a plurality of through passages, each through passage being formed by a rectangular part and a tapered part. Due to the plurality of through passages, partition walls are being formed between the through passages. Compared to U.S. Pat. No. 4,436,144, these partition walls contribute to an increased strength of the checker brick. The plurality of through passages also allow to increase the total contact surface between the gas and the checker brick, thereby increasing the heating surface for a better heat exchange.
Checker bricks similar to the one disclosed in U.S. Pat. No. 2,017,763 have been suggested, wherein the through passages have circular, square or hexagonal cross-section, the latter being particularly preferred because they allow partition walls of substantially uniform thickness. Checker bricks of hexagonal cross-section are also commercially known as checker bricks of the GSI type.